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temperature control system for that zone fails
to the full-cooling mode (30°F above ambient
temperature).
Pressure Regulating Shutoff
Valves
Each pressure regulating shutoff valve (PRSOV)
is a normally open electrically actuated solenoid
valve. Selecting either L or R with the
AIR SOURCE SELECT knob (Figure 11- 4) energizes
the opposite (left or right) PRSOV
closed, limiting bleed-air inflow to the cabin
from only the selected side. The left PRSOV is
powered from the right feed bus No. 2. If either
PRSOV loses power, the valve is spring-loaded
to the open position.
Flow Control Valves
Each FCV has two openings: one allowing 4
ppm of bleed air to pass through the system
from the corresponding engine, and the other
allowing 8-ppm flow. Normally, both valves
are deenergized to 4 ppm, for a total flow to
the cabin of 8 ppm.
If either engine fails, or the crew manually selects
cabin air supply from one engine only,
the FCV of the supplying engine opens to the
8-ppm setting.
If power to either FCV is lost, the valve is
spring-loaded to the 4-ppm position.
Duct Overheat Temperature
Sensors
The duct overheat temperature sensors are
downstream of the duct temperature sensors.
The sensor opens or closes in response to the
Figure 11-4. AIR SOURCE SELECT Knob
11-6 510OM-00
CITATION MUSTANG OPERATING MANUAL
temperature of the bleed air in the duct. When
closed, it sends a signal to the crew alerting
system (CAS), which displays the AIR DUCT
O’HEAT L (or R) message.
Duct Temperature Sensors
The duct temperature sensors are immediately
downstream of the FCV and upstream of the
overheat sensors. These duct temperature sensors
signal the temperature of the bleed air to
the zone PCB for that side.
Zone Temperature Sensors
The cockpit and cabin compartments each
have a zone temperature sensor that detects the
air temperature in that zone. The cockpit zone
temperature sensor is behind the pilot instrument
panel, below the cooling fan. The cabin
zone temperature sensor is in the aft evaporator
inlet (behind the aft cabin seats near the
floor of the cabin).
The environmental PCB compares this zone
temperature with bleed-air temperature reported
by the duct temperature sensors and crew settings
of the temperature control knobs to determine
necessary automatic changes to bleed-air
temperature.
Do not block the airflow at either of the zone
temperature sensors. Obstructions to airflow
causes errors in a sensor signal to its environmental
temperature controller, resulting in incorrect
temperature control for that zone.
CONTROLS AND INDICATIONS
Controls specifically for the cabin bleed-air
systems are on the ENVIRONMENTAL control
panel below the copilot primary flight
display (PFD) (Figure 11-5).
AIR SOURCE SELECT Knob
The AIR SOURCE SELECT knob is a rotary
electrical switch that selects the source(s) of
air entering the cabin. To do this, it controls
the PRSOVs and FCVs for the bleed-air ducts.
It also controls the fresh-air fan when the aircraft
is unpressurized.
OFF
The OFF position energizes both PRSOVs
closed. This stops all bleed-air inflow and
fresh-air inflow to the cockpit and cabin.
BOTH (Both Engines)
The BOTH position deenergizes both bleed-air
PRSOVs open, allowing temperature-controlled,
Figure 11-5. Environmental Control Panel
510OM-00 11-7
CITATION MUSTANG OPERATING MANUAL
pressurized bleed air to both cockpit and cabin
zones from their respective engines (left for
cockpit, right for cabin). This also deenergizes
both FCVs to 4 ppm, for a total flow of 8 ppm
to the pressure vessel.
NOTE
On the ground, when the AIR
SOURCE SELECT knob is set to
BOTH, if cabin temperature is greater
than 65°F and throttle position is less
than cruise detent, the environmental
PCBs automatically energize the
PSROVs closed. This prevents hot
air from entering a warm cabin.
L (Left Engine)
The L position energizes the opposite (right)
PRSOV closed. This limits bleed-air flow to
the pressure vessel from only the selected (left)
engine. The right (cabin) system PRSOV closes,
and bleed air flows to only the cockpit. Because
all bleed air flows aft through the cabin to the
outflow valves, cockpit air also supplies the
cabin. This also positions the left FCV to 8 ppm
for a total flow of 8 ppm to the pressure vessel.
R (Right Engine)
The R position energizes the opposite (left)
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Cessna塞斯纳公务机飞行手册(60)
